Hybrid Electric Vehicles are becoming more common. It is known to provide external speaker systems to generate vehicular noise when such vehicles are travelling under electric power in order to provide warning to pedestrians of the vehicle approach. In some jurisdictions this is even becoming legislatively mandated. However, the addition of external speaker systems to generate such noise adds to cost and vehicle complexity. It is an aim of the present invention to address this disadvantage.
It is known to provide noise modification systems in motor vehicles. Such systems typically comprise one of two types—Active Noise systems, in which one or more speaker units are fitted to exhaust systems or elsewhere in a vehicle such as in the occupant cabin, and Active Exhaust systems, in which typically one or more bypass valves are provided within an exhaust system to physically alter the flow path of exhaust gasses through different parts of the exhaust system.
The speakers in Active Noise systems, in conjunction with various control means and methods, are generally used to provide noise waveforms, usually related to and/or derived from the ‘natural’ noise generated by an Internal Combustion Engine (ICE) exhaust system and/or the ICE itself. These noise waveforms are typically used to ‘cancel out’, minimise or suppress native exhaust notes, but may also be used to enhance them. Minimising/suppressing/cancelling out of noise may be for the purpose of providing a quiet, ‘luxury’ driving experience for drivers or passengers of a vehicle, or to minimise external noise of the vehicle, possibly for legislative purposes. Enhancement may be for the purpose of providing a ‘sporty’ feeling to a driver and/or passengers of a vehicle and/or to provide a particular external noise to indicate the sportiness of a vehicle to bystanders.